Drillship global strength analysis under oblique equivalent design waves

Abstract

For the design of off-shore drillships, one of the criteria for initial strength assessment is based on global strength analysis under oblique equivalent design waves (EDW). The global strength procedure is based on an iterative approach, taking into account the ship hull external shape non-linearities, for a set of heading angles and design wave heights according to shipbuilding classification societies rules. This study analyzes the global strength of a drillship having 210 m length, for two relevant displacement cases. The numerical analysis is done by own code, delivering the ship-wave relative position and the generated wave loads. The results are compared to the limit values from several shipbuilding rules and the initial drillship strength is evaluated.

Keywords

• drillship, equivalent design wave, oblique waves, initial strength assessment.